Aerial ladder



L. M. HOARD ET AI.

AERIAL LADDER Feb. 26, 1963 4 Sheets-Sheet 1 Filed Feb. 23, 1961 INVENTORS.'- LEE M. HOA ED PA YMO/VD E fl MMEQ $0M? ATTORNEYS Feb. 26, 1963 L. M. HOARD ETAI.

AERIAL LADDER K. 0% 5 82M Y 2 RAn t M w w \R m a h I I CI T v wmp r m 1 N A w wk 0 h 5 S Lvl 4 U1 N\ A wv 2 Z@ NS Filed Feb. 2

Feb. 26, 1963 M. HOARD ETAL I 3,078,949

AERIAL LADDER Filed Feb. 23, 1961 4 Sheets-Sheet 3 UINVEZNTORSM 155 M, #01420 PAY/401w F. MAMEA A 1mm: rs

Feb. 26, 1963 L. M. HOARD ETAI. 3,07

AERIAL LADDER Filed Feb. 23, 1961 4 Sheets-Sheet 4 INVENTORS:- 45; M. Han/e0 2/1 mow F. MAM-5,2

United States Patent Cfifice attests Patented Feb. 26, 1963 3,78,9d9 AERIAL LADDER Lee M. Hoard, San Lorenzo, and Raymond F. Manner, Hayward, Salli, assignors to Utility Body Company, a corporation of California Filed Feb. 23, 961, Ser. No. 91,196 4 (Claims. (Ci. 182-2) This invention relates in general to extensible ladders or booms of the type employed to support a work platform or basket for use in elevated locations, such as for power line work, tree trimming, street light replacement and similar operations.

One object of our invention is to provide an adjustable power-operated aerial work ladder mounted on a mobile base such as a utility truck chassis and having a Work platform mounted on the extreme end of an extensible section for the support of a workman.

Another object is to provide an extensible aerial ladder which is power-operated and which can be fully controlled as to angular attitude, the degree of traverse through a full 360 and the amount of extension of a movable section of the ladder.

An additional object of the invention is to provide an extensible support for a work basket wherein the support platform is in a horizontal position at any angle of elevation of the ladder and this whether the movable ladder section is extended, retracted or is an intermediate position.

A still further object of the invention is to provide an extensible ladder of the mobile type having a safety mechanism incorporated which will prevent sudden tilting of the work platform from the horizontal in the event of failure of the positioning apparatus.

A further object of this invention is the provision for rotating the work basket into a stowed position wherein it is locked in place for convenience during transportation from one work location to-another.

Referring to the drawings:

FIGURE 1 is a side elevation of the extended ladder shown mounted on a truck, with several operating positions indicated in broken lines.

FIGURE 2 is a side view of the ladder assembly with certain portions cut away to show the compensating cable system.

FIGURE 3 is a plan view of the ladder assembly showing the extending motor and the brake mounting.

FIGURES 4 and 5 are enlarged partial sections of the lower ladder structure showing the provisions for mounting the extending chain assembly and the support rollers for the upper ladder.

FIGURE 6 is a partial section taken on lines 6-6 of FIGURE 4 with a rail of the upper ladder included to show the sliding guide means.

FIGURE 7 is an enlarged transverse section taken on line 7-7 of FIGURE 3 to show the construction of the upper ladder and its supporting rollers.

FIGURE 8 is a side view of the work basket and its mounting means.

FIGURE 9 is an end view of the upper ladder with portions cut away for purposes of illustration and also showing the stowage hold-down means.

FIGURE 10 is a side view partially in section of the basket positioning cable interconnection and safety means.

FIGURE 11 is a side view partially in section of the opposite basket support lever with cable tension control mechanism.

The invention as illustrated in the accompanying drawings covers an extension ladder assembly designated generally as it) rotatively mounted on a utility truck 11 of the type normally used as carriers for equipment of this type. A work basket or personnel support 12 is pivotally mounted in the outer end of the movable section 13 of the ladder assembly 10 to provide a level and horizontal support platform for a workman, regardless of the position of the ladder support means or the amount of extension of the movable portion of the ladder assembly. A cable assembly 14 is provided for this purpose as will be explained hereinafter. A supporting pedestal member 16 is mounted on the chassis structure 17 of truck 11 in the usual manner to provide rotatable support for the ladder assembly 10.

The lower or non-extensible section 18 of the ladder assembly 10 comprises a pair of metal side rails 19 and 21 having a plurality of rung members 22 fastened therebetween at spaced intervals. A cross rod 23 is also bolted to sleeve fittings 24 welded to side rails 19 and 21 toward their lower end (FIGURES 2, 3, and 4). Rod 23 passes through a horizontal tube member 25 fastened as by welding to a generally U-shaped bracket 26 mounted on the top of pedestal 16, thus providing pivotal support for the ladder assembly 10. A hydraulic cylinder 27 is pivotally mounted on pedestal 16 with its piston rod 23 connected to a pair of plates 29 welded to a heavy transverse member 31 fastened to reinforcing plate extensions 32 and 33 afiixed to side rails 19 and 21. Cylinder 27 controls the angle or elevational attitude of the ladder assembly 10 by pressure from a hydraulic pump not shown.

An electric motor, hydraulic motor, or other power source 36 (FIGURE 3) is connected to a speed reducing gear assembly 37, mounted on a bracket 38 affixed to side rail 21 for driving a transverse shaft 39 journalled on the lower ladder section by means of chain 41 trained about a sprocket on the speed reducing gear assembly 37 and one on shaft 39. A pair of sprockets 42 are fixed to shaft 39 to provide for driving a pair of chains 43 to extend or retract the movable section 13 relative to section 18. Each of the chains 43 engages an idler sprocket 44 (FIGURE 5) rotatably mounted in a clevis member 46 adjustably supported as by bolt 47 on rung 48. Inserted in each chain 43 is an elongated bar member 49 (FIGURE 4) bolted to a flanged plate 51 fastened to the structural portion of the plastic rails 71 and 72 of the extensible upper ladder assembly 13. Plastic strips 52 are also affixed to plate 51 to act as guide bearings for the movable section 13. Strips 52 bear against the inner surfaces of angle element 53 fastened to side rails 19 and 21 to provide sliding support for the inner end of movable section 13. Stops 54 are provided to prevent inadvertent over-travel of the extensible section.

To facilitate linear movement of the movable section, two pairs of horizontal mounted'rollers 55 and 57 and one pair of vertically mounted rollers 61 are provided. In addition, these being mounted adjacent the outer end of the lower or non-extensible section of the ladder. One pair of rollers 55 is rotatably fastened to brackets 56 (FIGURE 7) affixed to rails 19 and 21 while the second pair of rollers 57 is journalled between plates 58 welded to transverse tube 59 affixed to rails 19 and 21. The vertically mounted rollers 61 are rotatably supported in a forked element 62 pivotally mounted at 63 on a bracket 64. A threaded ball end bolt 65 provides for adjustment of the transverse spacing of these rollers for proper contact with the upper ladder section. A pair of handle elements 66 are welded to the outer surface of rails 19 and 21. A spring actuated band brake 67 is installed between bracket 68 on rail 19 and a drum 69 afiixed to the extremity of shaft 39 to provide a damper action on the ladder extending chain assembly 43 (FIGURE 6).

The upper or extensible ladder section 13 comprises a pair of elongated molded plastic side rails 71 and 72 having a plurality of spaced rung members 73 fastened thereto as by flanged fittings 74. In order to provide the required strength for rails 71 and 72, we have chosen to fabricate them of plastic impregnated fiber-glass wrapped around a rectangular wood filler 76 toward one edge and a preformed plastic tube 77' toward the other edge (FIGURE 6). The rectangular shape of the rail around the filler 76 provides flat surfaces to cooperate with the guide rollers 55, 56 and 57 previously mentioned. The tube 77 and its surrounding plastic are curved in a configuration to provide a hand rail for a workman.

The work basket or personnel support 12 is pivotally mounted at the extreme outer or upper end of rails 71 and 72 by means which assure that, whenever occupied and in use, the floor or platform of the basket is horizontal at all times and this no matter what the angular attitude of the ladder proper nor whether the movable section is extended or retracted or is at an intermediate position.

The basket assembly 12 is fabricated as by welding of formed tubing, braces and a support platform for a workman (FIGURE 8). An inverted U shaped member 81 of channel section is welded to a transverse tube 82 and serves as a support for the rectangular base frame 83 to which is aflixed an expanded metal floor plate 84. An upper looped tube member 85 is welded at its lower ends to member 81 and serves not only as a hand rail but also has afllxed thereto a pair of D shaped rings 86 to permit the attachment of a safety belt if desired. A looped tube member 87 of generally inverted U shape is affixed to the outer edge of frame 83 with its upper extremities welded to the bends in tube 85 to form forward upright rails and side bracing. A pair of angularly disposed tubes 88 and diagonal brace elements 89 are included to increase the strength and rigidity of the assembly.

As previously stated, the support member 81 of the basket assembly 12 is welded to a tube 82, which fits concentrically about a smaller tube 91 of greater length (FIGURE 9). Tube 91 has afiixed thereto toward its opposite ends a cable lever arm 92 and a spring lever arm 93, the purpose of which will be explained. Excepting when the boom is horizontal and the basket is stowed by being pivoted counter-clockwise, as seen in FIGURE 1, support 81 and cable lever arm 92 may be considered as extensions of one another, together constituting a single first class lever arm. Fastened between lever arms 92 and 93 is a tubular member 94 which engages the support member 81 and so serves as a stop for basket assembly 12 when the latter moves clockwise in FIGURE 1. The tube 91 is fitted about a longer central tube 96 which has a. ratchet Wheel 97 (FIGURE welded to one end and a mounting plate 98 welded to the other end after insertion into tubes 91 and 82 (FIGURE 9). The ratchet wheel 97 is bolted to rail 72 while the, mounting plate 98 is bolted to rail 71 securing tube 96 against rotation. However, tube 91 carrying lever arms 92 and 93 is. free to rotate in tube 96 while tube 82 supporting basket 12 may be rotated around tube 91 in a counter-clockwise direction (FIGURE 1), away from the stop member 94 for purposes of stowage as will be explained (see the lowermost position of the ladder in FIGURE 1).

Cable lever arm 92 has welded thereto an offset plate member 101 whereby a bifurcated end 102 (FIGURE 9) is provided for pivotal support at 100 of one end of link 103. Also Welded to lever arm 92 is a bracket extension 104 on which a pawl member 106 is pivotally mounted, as best seen in FIGURE 10. A tension spring 107 is fastened between arm 108 of pawl 1116 and a support clip 109 welded to lever arm 92. However, a spacer link rod 111 holds the pawl 106 in a disengaged position as long as there is tension on the cable assembly. In the event of cable failure, the link 103 rotates in a counter clockwise direction due to the action of spring 107 and so causes pawl 106 to engage immediately one of the teeth of ratchet wheel 97 to prevent any appreciable rotation of arm 92 and attached stop member 94. This effectively prevents any sudden tilting of the basket assembly 12.

A spring assembly 112 is mounted near the inner face of plastic rail 71 opposite to the cable lever arm 92 and acts to insure rotational movement of tube 91 through lever arm 93 as the ladder is elevated or lowered, as well as to maintain tension in the cable assembly at all times (FIGURES 9 and 11). Spring assembly 112 comprises a tubular housing 113, a plug 114 carrying a yoke 116 connected to an upright arm 117 welded to a ladder rung 73, a spring 118 and a sliding plunger element 119 with a yoke 121 connected to the upper end of arm 93.

A latching assembly 122 is mounted on the outer face of rail 72 to facilitate locking of the basket 12 in a stowed position during transportation. Angular guide members 123 and 124 are fastened to rails 71 and 72 for proper alignment of the basket 12. As shown in broken lines in FIGURE 1, stowage of the ladder assembly requires retraction of section 13 and positioning of section 18 in its lowermost or horizontal attitude to be caged in a support frame 126 mounted on truck 11. The basket 12 is rotated in a counter clockwise direction around tubular member 91 until the two lower portions of tube member slide over the guides 123 and 124. Spring latch mechanism 122 serves to lock the basket securely in this position. The latch 122 comprises an angular catch element 127 shaped to grasp the tubing 85 as at 128, and is alnxed to a U shaped member 129 pivotally attached at 131 to guide member 124 with a spring and bolt assembly 132 provided to hold it in the locked position.

The cable assembly 14 and its necessary adjuncts such as brackets, lever arms, pulleys, etc. is provided as stated for positioning the work basket in a horizontal attitude.

In actual fabrication of the ladder apparatus, we employ a pair of parallel cables as a safety precaution against possible mishap; this also permits the use of cables of a lesser diameter having more flexibility than a single large cable. However, for the purpose of simplicity, the assembly will be described as though a single cable were utilized.

The cable assembly 14 comprises (FIGURES 2, 3 and 7) essentially an inner looped flexible cable 136, a freefloating compensator 137 and an outer looped cable 138. The cable 136 is anchored at one end to an arcuate bracket 139 welded to transverse tube 25 mounted atop support pedestal 16. One end of cable 136 is bolted as at 141 to bracket 139. From this the cable passes over a guide pulley 142, around idler pulley 143 in compensator 137 and doubles back to an adjustable anchor assembly 144 supported on the inner end of rail 72 of the movable ladder section 13.

The outer cable 138 is anchored at one end to the non-extensible section 18 of the ladder by means of an adjustable cable end clevis fitting 146. From this the cable extends'around pulley 147 in compensator 137 and doubles back to pass through an opening 148 on side rail 72 and then thence to one end of tension insulator 149, this being pivotally connected at 150 to hinge member 103 of lever arm assembly 92. A pair of elongated rackets 151 support pulleys 152 for guiding the cable 133 through opening 148 in rail 72 (FIGURE 7). An examination'of FIGURE 2 will reveal that if the outer section 13 of the ladder assembly 10 is extended, there will be no resultant rotation of lever arm 92 (or of basket 12) since the free linear movement of compensator 137 will allow both cable members 136 and 138 to adjust to the change in location of their respective anchorages no matter what the relation lengthwise of the two ladder sections.

However, if the lower section 18 of the ladder is angularly displaced through movement of piston rod 28, the cable assembly 14 functions to rotate lever arm 92 and support member 81 with a resultant change in the position of basket assembly 12 with respect to the outer section 13 of the ladder assembly 10. Since the outer section 13 is accurately aligned by rollers and guides on section 18, the control of the positioning of the basket is positive. This action is essentially due to the placement and dimensions of the cable assembly 14 on the ladder sections 13 and 18, bracket 139 and lever arm 92. These form, in etfect, a parallelogram linkage through four relevant points: cable guide 142, transverse tube 25, pivot point 15% on hinge 1G3 and tube 96 about which lever arm 92 rotates. The upper side of the parallelogram is the cable assembly 14 and the lower side is the ladder assembly Ill and the geometry of the cables and compensator assures that the length of these two sides is always equal. The bracket 139 and the upper portion of lever arm 92 together with its hinge member 103 function as the other two sides of the parallelogram.

Thus, it will be apparent from the foregoing description, that we have provided a practical design for a mobile power-operated extension ladder having a work basket or platform mounted thereon in which, while in use, the floor is always positioned in a horizontal attitude, unaffected by the angular changes or extended condition of the ladder assembly.

We claim:

1. In a telescoping assembly having an upper and a lower section extensible with respect to one another, a personnel support basket mounted at the outer end of the upper section and rotatable fully from a work position into a stowing position in which the basket rests over said upper section, means for altering the position of said basket as the angle of said assembly to the horizontal is altered, and means for locking said work basket in position upon failure of said position altering means, said locking means including a fixed shaft providing a hinge mounting for the basket, a racheted wheel on said shaft, a pawl mounted cooperatively to the racheted wheel, and means controlled by the position altering means for releasing the pawl to engage the racheted wheel upon failure of said position altering means.

2. A telescoping assembly of the type adapted to be angularly raised and lowered about a horizontal axis and rotated about a vertical axis comprising:

( a rotatable pedestal;

(b) a lower boom section secured at the said horizontal axis to said pedestal;

(c) an upper extensible boom section mounted for telescoping movement relative to said lower section;

(d) a lever arm pivoted intermediate the ends thereof to the distal end of the said extensible boom section;

(e) the normally lowermost end of said lever arm being secured to one side of a horizontal work platform;

(f) means fixed to said pedestal providing an anchor;

(g) a compensated cable assembly secured at one end to the said anchor and at the other end to the said lever arm at a point thereon adjacent the normally uppermost end thereof, said compensated cable assembly consisting of two cables and a compensator having two parallel rollers secured together, one cable extending from the said uppermost end of the said lever arm about one roller of said compensator to said lower boom section and a second cable extending from the said anchor about the other roller of the said compensator to the said extensible boom section;

(It) the point of attachment of said compensated cable to the said anchor being spaced from the said horizontal axis a distance equivalent to the distance between the said intermediate point of the said lever arm and the point of attachment of the cable thereto whereby lines connecting the point of attachment of the said cable to the said anchor with the said horizontal axis and the point of attachment of the said cable to the said lever with the intermediate pivot point thereof are about equal and parallel.

3. A telescoping assembly of the type adapted to be angularly raised and lowered about a horizontal axis and rotated about a vertical axis comprising:

(a) a rotatable pedestal;

(b) a lower boom section secured thereto at the said horizontal axis;

(0) an upper extensible boom section mounted for telescoping action relative to the said lower boom section;

(0!) a lever arm pivoted intermediate the ends thereof to the distal end of the said extensible boom section;

(e) the normally lowermost end of said lever arm being secured to one side of a horizontal work platform;

(f) means secured to the said normally uppermost end of the said lever for controlling the angle of said lever arm relative to said extensible boom section;

(3) means fixed to said pedestal providing an anchor for the said lever arm controlling means;

(It) said lever arm controlling means being fixed to said anchor at a point thereon spaced from said horizontal axis a distance equivalent to the distance between the said intermediate pivot point of the said lever and the said point of attachment of said lever controlling means whereby lines connecting said horizontal axis with said point and said lever arm intermediate point with said lever arm uppermost point are parallel and equal in length;

(i) and an automatic latch mechanism operable on failure of the said lever controlling means for locking said platform in a horizontal position against rotatron.

4. A telescoping assembly of the type adapted to be angularly raised and lowered about a horizontal axis and rotated about a vertical axis comprising:

(a) a rotatable pedestal;

(b) a lower boom section secured thereto at the said horizontal axis;

(c) an upper extensible boom section mounted for telescoping action relative to the said lower boom section;

(d) a lever arm pivoted intermediate the ends thereof to the distal end of the said extensible boom section;

(2) the normally lowermost end of said lever arm being secured to the side of a horizontal platform nearest the upper extensible boom section;

(1) means secured to the said normally uppermost end of the said lever for controlling the angle of said lever arm relative to said extensible boom section;

(g) means fixed to said pedestal providing an anchor for the said lever arm controlling means;

(- said lever arm controlling means being fixed to said anchor at a point thereon spaced from said horizontal axis a distance equivalent to the distance between the said intermediate pivot point of the 7 said lever and the said point of attachment of said lever controlling means whereby lines connecting said horizontal axis with said point and said lever arm intermediate point with said lever arm uppermost point are parallel and equal in length;

(i) an automatic latch mechanism operable on failure of said lever arm controlling means for locking said platform against rotation toward the underside of said upper extensible boom section;

(j) and resilient means fixed at one end thereof to said upper extensible boom section and at the other end to said platform;

(k) said resilient means being oriented to resist pivoting of said lever arm in a direction away from the underside of said upper extensible boom section.

References Cited in the file of this patent UNITED STATES PATENTS 

4. A TELESCOPING ASSEMBLY OF THE TYPE ADAPTED TO BE ANGULARLY RAISED AND LOWERED ABOUT A HORIZONTAL AXIS AND ROTATED ABOUT A VERTICAL AXIS COMPRISING: (A) A ROTATABLE PEDESTAL; (B) A LOWER BOOM SECTION SECURED THERETO AT THE SAID HORIZONTAL AXIS; (C) AN UPPER EXTENSIBLE BOOM SECTION MOUNTED FOR TELESCOPING ACTION RELATIVE TO THE SAID LOWER BOOM SECTION; (D) A LEVER ARM PIVOTED INTERMEDIATE THE ENDS THEREOF TO THE DISTAL END OF THE SAID EXTENSIBLE BOOM SECTION; (E) THE NORMALLY LOWERMOST END OF SAID LEVER ARM BEING SECURED TO THE SIDE OF A HORIZONTAL PLATFORM NEAREST THE UPPER EXTENSIBLE BOOM SECTION; (F) MEANS SECURED TO THE SAID NORMALLY UPPERMOST END OF THE SAID LEVER FOR CONTROLLING THE ANGLE OF SAID LEVER ARM RELATIVE TO SAID EXTENSIBLE BOOM SECTION; (G) MEANS FIXED TO SAID PEDESTAL PROVIDING AN ANCHOR FOR THE SAID LEVER ARM CONTROLLING MEANS; (H) SAID LEVER ARM CONTROLLING MEANS BEING FIXED TO SAID ANCHOR AT A POINT THEREON SPACED FROM SAID HORIZONTAL AXIS A DISTANCE EQUIVALENT TO THE DISTANCE BETWEEN THE SAID INTERMEDIATE PIVOT POINT OF THE SAID LEVER AND THE SAID POINT OF ATTACHMENT OF SAID LEVER CONTROLLING MEANS WHEREBY LINES CONNECTING SAID HORIZONTAL AXIS WITH SAID POINT AND SAID LEVER ARM INTERMEDIATE POINT WITH SAID LEVER ARM UPPERMOST POINT ARE PARALLEL AND EQUAL IN LENGTH; (I) AN AUTOMATIC LATCH MECHANISM OPERABLE ON FAILURE OF SAID LEVER ARM CONTROLLING MEANS FOR LOCKING SAID PLATFORM AGAINST ROTATION TOWARD THE UNDERSIDE OF SAID UPPER EXTENSIBLE BOOM SECTION; (J) AND RESILIENT MEANS FIXED AT ONE END THEREOF TO SAID UPPER EXTENSIBLE BOOM SECTION AND AT THE OTHER END TO SAID PLATFORM; (K) SAID RESILIENT MEANS BEING ORIENTED TO RESIST PIVOTING OF SAID LEVER ARM IN A DIRECTION AWAY FROM THE UNDERSIDE OF SAID UPPER EXTENSIBLE BOOM SECTION. 